Exhaust device for indirect-heated gas-pired



May- 6, 1930. E. o. ENGELS 1,757,361

EXHAUST DEVICE FOR INDIRECT HEATED GAS FIRED OVENS AND THE LIKE Filed Oct. 13, 1928 I 'll BZ ower I N VEN TOR Ez qerze Oscar Engels ATTORNEY i Patented May 6, 1930 untrue STATES PAEENT OFFICE EUGENE OSCAR ENGELS, F SAGINAW, MICHIGAN, ASSIGNOB TO BAKER PERKINS COMPANY, INC., OF SAGINAW, MICHIGAN, A CORPORATION OF NEW YORK V EXHAUST DEVICE FOR INDIRECT-HEATED GAS-FIRED OVENS AND THE LIKE Application filed October 13, 1928.

This invention relates to bake ovens and pertains more particularly to gas-fired bake ovens of the indirect-heated type wherein gas burners are enclosed in pipes or condults that confine the gaseous products of combustion and conduct them to a point outside the oven and usually outside the building in which the oven is located.

The purposes of the present nvention are to provide a means for preventing damageto the oven and possible breakage of the windows of the buildings and injury to persons, all of which bad efiects heretofore have been produced occasionally by explosions of gaseous mixtures that have become trapped in the burner-enclosure or in the pipes that lead from the burners to the outside air. Explosions have sometimes been caused by premature or accidental ignition of the burners 2 while the exhaust pipes in communication with the burners contained combustible gases which, accidentally or carelessly, had been permitted to escape from the burners and to fill the burner jackets and the exhaust pipe. Sometimes sparks coming into contact with such vagrant explosive gases at or near the exhaust outlet caused similar explosions.

Another object is to prevent avoidable losses of heat from the oven after the burners 3 have been turned oif. Such heat losses have generally occurred because the natural draft or suction of the hot exhaust pipe was suflicient to draw large quantities of hot gases from a the burner pipe housings after the burners have been turned 0E. By preventing the withdrawal of large quantities of hot gases from the burner pipes of the baking chamber it is possible to continue the baking operation for some time after the burners have been turned off, thus utilizing the heat and saving fuel.

A stillfurther object is to avoid the undesirable effects of moisture accumulating in the exhaust pipe and in the conduits leading into it from the burners.

Heretofore such moisture accumulated in the exhaust pipe and sometimes flowed back through the connecting conduits to the burners, causing damage to them and im- Serial No. 312,288.

proper functioning when the oven was heated up the next time.

A still further object is to do away with the necessity of employing natural draft in the exhaust pipe and instead employing a forced draft which permits the use of relatively small exhaust pipes.

Heretofore the natural draft exhaust pipes necessarily had to be of relatively large diameter, said, five inches and larger, whereas my present improvement permits the use of exhaust pipes of much smaller diameter and consequently less costly.

An additional advantage of my improved exhaust pipe draft arrangement is that an exhaust pipe of considerable length can be employed without impairing its efiieiencyn I frequently employ exhaust pipes fifty and even one hundred feet long with several bends or turns in them in order to meet the requirements of the installation, whereas with natural draft the use of bends became a serious detriment to the draft, and any great length for the exhaust pipe also was practically out of the question.

lVith the foregoing and certain other objects in view, which will appear later in the specification, my invention comprises the devices described and claimed and the equivalents thereof.

In the drawings Fig. l is a diagrammatic top plan view showing part of the length of an indirect gas-fired oven with my improvement applied thereto.

Fig. 2 is a sectional side elevation of the parts shown in Fig. 1, the air supply header and its connections to the blower being omitted.

Fig. 3 is a detail view of the restricted section of the exhaust pipe.

As is clearly shown in the drawings, the baking chamber 1 contains the usual combustion iackets or conduits 2 characteristic of in direct heated ovens, andcontaining the usual gas burners 3. Gas is supplied to the burners through a feed header 4 which receives its supply from a mixer in the usual way, the mixer being supplied with gas from any suitable source and with air through a pipe 5 from the blower located in any convenient place. The burned gases from burner 3 pass along the circuitous pipe2 which is an extension of the combustion jacket and are delivered into an exhaust header 6, by means of a connection member 6 which is connected to a pipe 7 leading to a point outside the oven wall. Ordinarily this pipe 7 has an atmospheric outlet at some point outside the build= in applying my improvement to an oven arrangement of the kind described I provide at some suitable point along the length of pipe 7 an air supply, the air being under sufficient pressure to thoroughly dilute and sweep out from the outboard length of the exhaust pipe the exhaust gases which arrive at that point from all of the connected burners. The outboard end of the exhaust pipe, as 8, may be of any desired length to deliver the mixture of burned gases and air to the atmosphereat some safe and convenient place outside the building. The air supply may be brought through a pipe 9 Which connects with the supply of air under pressure produced by the blower that also supplies themixer with air. Preferably I provide in the exhaust pipe 8 an inspirator nozzle, and near the nozzle reduce the diameter of the pipe 8, as indicated at 10 in Fig. 1,

It isnow evident that when the blower is started and begins to supply air to the mixer a certain amount of compressed air will simultaneously commence to discharge into the exhaust pipe. The immediate effect is to dilute whatever gases have remained in the exhaust pipe, whether they be burned gases or combustible gases that have accidentally been allowed to accumulate there. Such dilution immediately reduces or destroys the explosive properties of the gas that may have been entrapped in the exhaust pipe and its connections. Even if the jackets 2 happen to be filled with explosive gas and through accident the burners are ignited the resulting explosion will be very slight and can do no damage because of the small amount of explosive gas involved, whereas heretofore most of the injury arose from the fact that an exhaust pipe of large volumetric capacity connected to the jackets would store a dangerous quantity of gas whose explosive force would be added to that of the gas in the jackets 2.

Since the air injected into the discharge pipe forcefully sweeps out the burned or unburned gases, as the case may be, at a relatively fast rate the exhaust pipes can be small and their reduced volumetric capacity fur ther provides a safety factor against dangerous explosion.

When the exhaust pipe is reduced in diameter, as at 10, to provide the desired inspirator effect it so throttles the gas passage from the exhaust header6 and pipe 7 into the exhaust pipe 8 that whatever heat remains in the pipe 8 after the burners have been turned ofi will have little or no effect in the way of producing a draft that can carry off very much of the hot gases remaining in the burner enclosure pipes 2. Y

Heretofore, with natural draft and large pipes the heat of the exhaust pipe would create such a draft as to allow the burner heat to be rapidly dissipated and the heat content of the gases in the jackets was consequently wasted,

In practice the reduced section 10 of pipe 8 and its inspirator is located as close as possible to the oven, but as above stated, the exhaust pipes 8 may be as long as necessary and may contain a number of bends or turns without materially impairing the e-fiiectiveness of operation.

I have described the air supply pipe 9 as taking its'source at the blower and this is the preferable arrangement, because the dilution and sweeping out of the gases from the discharge pipe 8 starts and stops automatically with the starting and stopping of the gas mixer and with the igniting and turning out of the burners. I

It is notnecessary, however, for the fundamental operation of the invention that the air supply pipe 9 shall take its source from the blower and thus operate automatically. It can be connected to any other source of air under pressure, in which latter event the attendant must start andstop the air supply to the exhaust pipe whenever occasion requires.

By the means above described I have ac-- complished all the results setforth in the statement of invention and have produced an exhaust gas system for enclosed-burner type ovens and the like that is not only much safer than the natural draft arrangement'ordinarily used, but is cheaper to install, is more positive in operation, more economical in fuel, and, by reason of the fact that dry air or its equivalent blown into a heated pipe has a pronounced drying efiect, moisture troubles with the burners are entirely eliminated and such accessories as drip cocks for carryingofl water of condensaiton are rendered unnecessary.

While I have described the operation of the invention as employing atmospheric air for dilutingithe gases in the exhaust pipe, it is obvious that any other gas of non-explosive character, dry steam, for example, can be employed without departing from my invention as herein claimed.

Having thus described my invention, what I claim and desire to secure by Letters Patent 1. In combination, a bake oven, an enclosed gas burner heating system therein, a source of non-inflammable gas under pressure, a pipe connecting said source with the exhaust pipe from said burner system, a second pipe connecting said source, through a gas-air mixer,

with the various burners of said oven heating from said header,

system.

2. In combination, a bake oven, a plurality of enclosed gas burners therein, a waste gas header common to said enclosed burners, a blower for producing non-inflammable gas under pressure, a pipe connecting the delivery side of said blower with a waste gas pipe a second pipe connecting said blower, through a gas-air mixer, with the various burners of said oven heating system, for the purposes set forth.

3. In an oven having a gas burner therein, a waste gas conduit from said burner, a source of air under pressure, pipes connecting said source respectively with said waste gas conduit and said burner, a source of com bustible gas connected to said burner, and means for simultaneously supplying air from said source to said waste gas conduit and to said burner, for the purposes set forth.

In testimony whereof, I aifix my signature.

EUGENE OSCAR ENGELS. 

